Resize FZF window when vim resizes

[rmartine-ias]

Checklist

• I have fzf 0.54.0 or later
• I have searched through the existing issues

Output of :echo system(fzf#exec() .. ' --version')

0.65.1 (e5cd7f0a)

OS

• Linux
• macOS
• Windows
• Etc.

Problem / Steps to reproduce

I use vim inside tmux. Often, I want to find uses of some function. When I :Rg, sometimes the results get cut off so much that they're not helpful. I maximize the tmux pane, but the fzf window doesn't resize, so I have to relaunch it and type my search again. This is annoying. See video:

Screen.Recording.2025-09-08.at.1.02.06.PM.mp4

Desired solution: when vim resizes, the fzf panes should redraw and fill the newly available space.

[junegunn]

I'm not sure if Vim provides an API to resize a popup window. If it doesn't, we're out of luck.

A better option I think (which I use) is to make fzf start in a tmux popup instead of a vim popup, so it can be larger than the current pane, by setting g:fzf_layout option like this:

if exists('$TMUX')
  let g:fzf_layout = { 'tmux': '90%,60%' }
endif

(reference: https://github.com/junegunn/fzf/blob/master/README-VIM.md#starting-fzf-in-a-popup-window)